Production of improved catalyst-type particles using length and density grading

Abstract

A spent hydrotreating catalyst having carbonaceous and metallic deposits comprising generally cylindrical, free flowing particles of regular geometric shape having substantially the same diameter but of varying length is stripped, length graded, density graded using an upward flow of gas through an inclined, vibrating surface, and regenerated to achieve catalyst activity very near that of a fresh catalyst.

What is claimed is: 
     
       1. A process for treating a spent hydrotreating catalyst supported on a refractory metal oxide support comprising shaped, generally cylindrical, regular geometric particles having substantially the same diameter, varying length and an L/D greater than one, said spent catalyst particles having carbonaceous and metallic deposits resulting from a hydrocarbon feedstock; passing said spent catalyst particles to a stripping zone in which volatilizable hydrocarbons are stripped from said withdrawn spent particles to render said catalyst particles free-flowing;   passing said free-flowing catalyst particles to a length grading zone comprising a rotating cylindrical drum having inwardly opening indentations in a cylindrical wall thereof, said indentions having a transverse diameter L 1  in the range of 0.8 to about 24 millimeters;   rotating said drum about a longitudinal axis thereof at a speed sufficient to entrap in the indentations and convey catalyst particles having a length below L 1  and an L/D greater than one upwardly to a height permitting the catalyst particles to fall into a fixed upwardly opening trough, while retaining catalyst particles having a length above L 1  and an L/D greater than one in a bottom portion of said drum; conveying the catalyst particles in the trough out a first outlet;   whereby said catalyst particles with a length less than L 1  are separated from the desired catalyst particles which have a length greater than L 1  ; said particles having a length greater than L 1  comprising lightly contaminated particles and more heavily contaminated catalyst particles; and   passing said catalyst particles from said bottom portion of said drum to a density grading zone in which lightly metals contaminated catalyst particles become suspended in a gas above more heavily metals contaminated catalyst particles, said more heavily contaminated catalyst particles being caused to move upwardly along an inclined, vibrating surface and are thereafter collected at a first density grading zone outlet, said lightly contaminated catalyst particles contacting a lower portion of said vibrating surface and are collected at a second density grading zone outlet; and   passing said lightly contaminated catalyst particles to a regeneration zone in which carbonaceous deposits are removed from said lightly contaminated catalyst particles by oxidation in the presence of an oxygen-containing gas to produce regenerated catalyst particles which are lightly contaminated with metals.   
     
     
       2. The process of claim 1 wherein the particles in the bottom portion of the drum have an L/D between 1.0 and 2.0. 
     
     
       3. The process of claim 1 wherein said metallic deposits comprise nickel and vanadium. 
     
     
       4. The process of claim 1 wherein said spent hydrotreating catalyst is nickel molybdate on a refractory metal oxide support. 
     
     
       5. The process of claim 1 wherein L 1  is in the range of 0.8 to about 6 millimeters. 
     
     
       6. The process of claim 4 wherein said refractory metal oxide support is alumina. 
     
     
       7. The process of claim 1 wherein lightly contaminated catalyst particles are passed from said second density grading zone outlet to a rejuvenation zone wherein said catalyst particles are acid leached to remove undesired metals from the catalyst particles, and the rejuvenated catalyst particles then passed to said regeneration zone. 
     
     
       8. The process of claim 1 wherein said spent catalyst particles are stripped in said stripping zone with an inert gas at a temperature of from about 100° to about 500° C. 
     
     
       9. The process of claim 1 wherein said lightly contaminated catalyst particles are contacted in said regeneration zone with an oxygen-containing gas at a temperature of from about 200° to about 700° C. to produce regenerated catalyst particles lightly contaminated with metals. 
     
     
       10. The process of claim 1 wherein at least about 80 percent of said catalyst particles with a length less than L 1  are separated from the desired catalyst particles which have a length greater than L 1 . 
     
     
       11. The process of claim 1 wherein said lightly contaminated regenerated catalyst particles are passed to a hydrotreating zone.